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.UNITED sTATEspiirnnT- OFFICE.

` SVEN' HULDT, 0F STOCKHOLM, SWEDEN, ABSIUN'OR T0 NORSK ELEKTBISK HETAIJIN- UN'DLKKEN, SARPSBOBG, NORWAY.

METHOD 0F BEFIN ING ZINC.

Y i Bpecication of Letters Patent.

Patented Aug. 5,I 1919.

. Application inea api-usuari. semina. 15am.

The present invention has for its objectA to provide an improved method of refining zinc, whereby refined zinc of the desired degree of purity is obtained with economy in heat and in a continuous manner.

The refining operation according to the present invention is carried out continuously, by the employment of radiant heat produced by .electrical means and by employing special means for obtaining zinc of great purity, uniformity in operation of the refining process and economy in the amount of current consumed.

In the accompanying drawing Figure 1 is a transverse section and Fig. 2 a longitudinal section of a furnace for refining zinc according to the'present invention, proporabove indicated.

tioned as above described. The zinc to be refined is assumed to contain 0.5% of lead, and the bath surface is given the size of 0.5. square meters. 1 indicates the furnace, and 2 the electrodes projecting through openings in the furnace walls, and establishing an arc for heating the zinc bath contained in the furnace. 3 indicates a receiver in communication with the furnace chamber at the bottom thereof, and serving as a sealed inlet, through which the zinc to be refined is fed into the furnace chamber; 4 indicates the esca e operiing for the refined zinc vapors. In t is furnace the depth of the zinc,bath 5 is 5 centimeters." 6 is atapping hole. for drawing off the lead layer 7, gradually gathering on the bottom of the furnace chamber, so that the superposed layer of zine 5 will approximately maintain its depth Figs. 3 and 4 are views similar to Figs. l and 2, illustrating a furnace for refining zinc containing 15% lead. Similar letters refer to correspondin parts. The depth of the zine bath in this urnace will be 1D0 centimeters.

It will be found by tests, that the escaping zinc vapors contain lead, the feed of raw material should be augmented so as to establish a thicker layer of zinc.

' Obviously the drawing oil' 0f lead will be done without interfering with the process of bath is used.

refining, the heating being continuous, to effect continuous distillation.

Hitherto it has been assumed, that when refining zinc the source of heat will be most economically utilized, if the depth of the molten zinc bath, from the Surface of whichs the zinc is vaporized, is reduced as muchas possible. Vposed according to one known process o fining, to cause the molten zinc to ow in a thin layer from a. superposed receiver along an inclined plane, heating said layer during its fiow so as to vaporize the zinc.

The present invention however` which is based on extensive investigations and experiments in connection with the refining of zinc in electric radiating furnaces, consists in carrying-out the refiningpperation b employing a molten mass of zinc, whic is proportioned and calculated sufiiciently great, that the same constitutes a heat magazine or accumulator, sufficiently large to counterbalance considerable variations of temperature. It has been` found, that the zinc bath in ordinary `recesses of refinin zinc is subject to consi er'able variations o temperature, which have an unfavorable in- For this'v purpose Vit has been- 1pmfluence upon the uniformity of'the refiningthat the whole process is more economical,

owing to the said capability of the zinc bath to accumulate heat, than when'ia smaller Further, according to the invention, th depth of the zinc bath is proportioned in Yrelation to its surface in such a manner, that lead which is `always contained in the material to be'refincd, is prevented from being.

distilled during the refining operation.- Said depth is proportioned relatively to the furnace capacity by experimentally employing' several zinc baths of different depths and testing the zinc distilled from such baths.

If the zinc vapors thus distilled contain lead,

the depth of the zinc bath employed is too small and should be augmented by augmenting the feed of ruw material, until lead is n o longer present lin the v ors. This 1s a er1- terion of the fact, that t e layer of lead deposited on the bottom of the furnace, underneath the zinc layer is not heated by the superposed zinc layer to the temperature of distillation.

By the term de th of the bath above used is understood t ie depth of the bath at the shallowest place, if the bottom of the furnace is inclined, es toward a tapping place.

By means of the process above described zinc practically free from lead and other impurities, having a purity of 99.9%, may he obtained.

As an example of the proportions above referred to, it may be mentioned that for refining impure zine containing 0.5 to 15'% of lead, the bath surface may be a given size of 0.5 to 9 square meters and the depth of the zinc bath may be from 5 to 100 centi meters.

Having now fully described my invention what I claim is.

d1. The method of continuously refinin impure zinc by exposing the molten body o zinc to the action ofadiant heat predial-ed by electrical means` which comprises umilitaining a. body of zinc having such a depth in Vproportion to the vaporizing surface` that, lead from the layer of lend deposited under neath thc zinc layer, will renmin entirely un volatilized, whereby pure zine, free from tutes a heat magazine adapted to counter l balance variations of ten'ipcruture created by the source of heat, while distilling nl? pure zinc from the charge.

In testimony whereof I have signed my name t0 this specification in the presence of two subscribing witnesses.

S VEN H UL DT.

Witnesses:

WAmnMA BoMAN, GRETA Puur.. 

